Method of removing the solvents from solutions of resilient substances



A. KAMPF ER May 14, 194

METHOD OF REMOVING THE SOLVENTS FROM SOLUTIONS OF RESILIENT SUBSTANCES Original Filed Jan. 23, 1935 Patented May 14, 1940 v STANCES Y'THOD F REMOVING THE SOLVENTS ROM SOLUTIONS OF RESILIENT sun- Adolf Kampfer, Charlottenburg, Berlin, Germany Original application January 23, 1935, Serial No. 3,152. Divided and this application February 25, 1937, Serial No. 127,800. In Germany January 23, 193% 6 Claims. (01. 34.44)

This invention relates to the art of making laminated or "safety glass in which relatively thick layers of resilient transparent substances, usually of a resinous character, are disposed between sheets of glass, and particularly to'l'aminated glass in which the layers initially consist of solutions of resilient substances, the present application being a division of my prior application for patent filed on January 23, 1935, Ser. No. 3,152. In this method of producing laminated glass, the semi-liquid material is poured onto the glass in a relatively thick layer and it is necessary that the sheet of glass with the layer be disposed in an enclosed space or chamber and be subjected, While the solvent is evaporating, to the action of an atmosphere charged with vapors of the solvent so as vto keep the surfaces soft and thus permit of the escape from the layer of rising bubbles of gas or vapor.

This method is open to the objection that the amount of air enclosed within the chamber is invariable and is at a constant temperature. Being at a constant temperature, the air within the chamber is only capable of absorbing a definite and limited amount of the solvent vapors up to complete saturation and hence a complete removal of the solvent is only possible if the quantity of solvent in the layers is less than the power of absorption of the air. A second objection to which the former method is open is that with increasing saturation of the air within the chamber, the evaporation of the solvent is increasingly retarded. Thus the old process requires considerable time and the process is furthermore objectionable because the point at which the solvent has been completely expelled from the layer or the point at which the air in the chamber has been completely saturated with solvent vapors is extremely dificult to determine. Because of the length of time required, there is always the danger that the layers will be softened from the outside up to the point of deliquescence.

By my invention, the air in the chamber, after or prior to its saturation with the solvent vapors, is partly replaced by fresh air at the same temperature, until the solvent has been completely removed from the layer. In addition, my improved process provides for increasing the power of absorption of the air by either a constant and gradual increase in the temperature of the air or by a step by step increase.

I further contemplate that if there shall be repeated substitution of unsaturated air for saturated air and also there shall be a steady or step by step increase in temperature, the increase in being utilized for automatically controlling the escape'of part of the solvent laden air and the inlet of fresh air at the same temperature, thus accelerating the evaporationof the solvent and avoiding any excessive softening of the layers.

Other objects and advantages will appear more fully hereinafter.

An apparatus for carrying out my process is illustrated in the accompanying drawing wherein:

Figure 1 is a diagrammatic longitudinal section of this apparatus,

Figure 2 is a transverse section on the line 22 of Figure 1.

Figure 3 is a diagrammatic section through the inlet and outlet controlling valves.

Referring to the drawing, l designates a casing divided by horizontal partitions 2 into a plurality of superimposed horizontal open-ended chambers 3 designed to receive the sheets of glass 4 with the semi-liquid layers of transparent resilient material 5 thereon. As shown, there are three of these chambers 3, but it is to be understood that any number of chambers may be provided. Each chamber 3 is capable of being tightly closed at its opposite ends by doors 6 and 6 orby other suitable means, and each chamber encloses a heating device such, for instance, as a serpentine steam pipe I. The floors 2 for the several chambers may be covered each with a sheet of glass so as to obtain an exactly fiat floor. In front of the casing l opposite to the entrance openings of the chambers 3, there is disposed a horizontal, table 9 which is vertically adjustable by any suitable means so that it may be moved successively'into the planes of the floors of the several chambers. Above the table 9, there is provided means 10 of any suitable character which serves for the application of the plastic solution to the single sheets of glass, this solution discharging. means being mounted upon the supports H. It is designed that the sheets of glass to be covered with the plastic layers shall be placed upon the table 9, then conducted below the device l0 and finally passed into the selected chamber 3.

Various means may be employed for conveying sheets of glass from the table 9 into the chamber and I have illustrated for this purpose a web l2 of paper or other sheet material which is drawn over the table and through the particular chamber to be charged. This web is withdrawn from a supply roll l4 and is deflected over the face of the table by means of the roller 15. The glass td be coated with the layer of plastic have been freed of their solvents, the outlet door 6 is opened and the sheets of glass withdrawn from the chamber by the assistance of the paper web. These sheets of glass may be discharged upon an endles conveying belt I! which is, of course, intended to be adjustable as regards height, so as to be disposed opposite the selected chamber.

Each chamber 3, as shown in Figure 2, is provided with an outlet pipe 20 for the solvent vapors and for the air contained within the chamber. The outlet pipe 20 has disposed in its length a valve casing 2| with a coacting valve 2|*- which opens automatically upon the pressure of the mixture of air and vapor contained within the chamber rising to a certain predetermined degree. The outlet pipes'20 all open into a common pipe 22 by means of which the solvent saturated air is conducted to a condenser 23 in which the solvent may be recovered.

Also extending into each of the chambers 3 are supply pipes 25 by which fresh air is discharged into the chambers. The several pipes 25 extend from a header 26 connected to an air pump 21 driven by an electric motor 28. The header 26 is connected to a manually regulatable' heating device shown as an electric heater and designated 29 by which the fresh air introduced into the chambers may be preheated to any desired temperature. It will be noted that the outlet opening of each pipe 25 is disposed adjacent one end of the chamber 23 while the inlet opening of the corresponding pipe 2|] is disposed adjacent the opposite end of the chamber 3.

Each fresh air inlet pipe 25 opens into a valve casing 30 having a valve seat therein and coacting with a valve 3|] as shown in Figure 3. The valve 2| is connected to the valve 3|] by means of a yoke 3|, thus the two valves 2| and 30- are opened or closed simultaneously. Associated with each yoke 3| are two contacts 32 adapted, when the yoke is raised and the valves are opened, to be bridged and electrically connected by the yoke. One of these contacts 32 is connected to the power line a. while the other contact 32 is connected by the conductor b to an electric motor 28 in turn connected by the conductor 0 to the line wire d. Of course, all of the contacts 32 are connected in series to the power line a. by wire e. Thus upon a common opening movement of the two valves 2| and 3|] the motor circuit is completed and the air pump is operated. If, therefore, the outlet valve 2| of the particular chamber being used is opened, there occurs simultaneously the opening of the air inlet valve 30 and preheated air is forced into the chamber. The heating element I of each chamber is provided outside of the casing with a supply pipe 33 and each heating element is connected to this supply pipe through a valve casing 34 provided with a valve for regulating the heating effect. By this means, the temperature of each chamber may be increased very gradually or step by step in such a manner that complete saturation of the air in the chamber with the solvent vapors escaping from the plastic layer on the sheet of glass is never quite reached.

In the operation of this mechanism and in the carrying out of my process, the sheets of glass with the plastic layers thereon are carried into the corresponding chamber 3 and the doors thereof closed. Evaporation of the solvent immediately starts and the atmosphere within the chamber becomes more and more laden with solvent. At the same time, the temperature of the chamber is gradually increased. This increases the pressure within the chamber and this pressure, when it reaches a predetermined degree, forces open the valve 2| and simultaneously causes the opening of the valve 3|! and the automatic starting of. the motor and consequently the automatic introduction of heated fresh air into the chamber. Thus the saturated air is carried off and fresh heated air is carried into the chamber until the pressure within the chamber falls, whereupon the valves 2| and 3| close and the circuit to the motor is broken so no more fresh air is pumped into the chamber until the pressure within the chamber has again risen to a point where the valves 2| and 3| are again opened. Thus it will be noted that when a certain pressure within the interior of the chamber has been obtained, a part of the mixture of air and vapor is discharged from the chamber and replaced by fresh preheated air. Thus the layer of plastic substance on the sheet of glass is maintained in an atmosphere charged with vapors of the solvent so that formation of a skin on the surface of the layer is prevented and the absorptive power of the atmosphere is gradually increased until either the point of saturation is reached or prior to this time when a part of the saturated vapors are withdrawn and fresh heated air admitted in quantities sufiicient to replace the saturated gas or air to thus reduce the pressure and temperature of the air or gas. By intermittently withdrawing the saturated vapors and intermittently admitting fresh heated air, I prevent the formation of a skin on the surface of the layer while very greatly reducing the time necessary for curing" this layer.

It is to be understood that the atmosphere above the layer to be treated must never be completely removed, at least, it must not be completely substituted by fresh air heated or unheated, on account of the fact that such fresh air, entirely devoid of solvent vapors, would produce a surface skin on the layer and this skin would be an obstacle in the way of removing the bubbles from the layer. Likewise there must not be a circulation of the air in the chamber over the layer or the same result will be brought about. What takes place within each chamber 3 is that as a result of the presence of the heating elements there is substantially a vertical rising movement of the air which exerts an action upon the bubbles of the solvent, within the mass under treatment, which accelerates the withdrawal of the solvent from the mass. The cooler portion of the air volume slowly descends from the plane of the heating tubes 1. On approaching these heating tubes the downward movement of the air is checked and there is a tendency for it to be reversed. Below the heating tubes 1 there is never a perceptible up and down movement in the air volume which contacts the mass under treatment. While there is this gradual vertical shifting of the air as the warmer saturated strata tends to rise and the cooler portion tends to move downward, there is no actual circulation movement of the air over the surface of the mass and as a result of this there is no tendency for the formation of a skin on the mass as there would be if a constant movement or circulation of air were effected through the chamber over and in con-,- tact with the surface of the mass of material. The degree of vertical movement of the air in the chamber is so slight that the air might be stated as being substantially stationary or quiescent. There is no actual forced movement of the air within the chamber in the area immediately above the mass of material. The only movement which takes place is that resulting from the setting up of convectioncurrents as a result of the heating of the air and the tendency of the heated air to change places with the coolerair above it. A mass having comparatively high viscosity produces a very tough surface skin on its first contact with air whether the air is heated or unheated.

If the mass is in the form of a hair or filament or the layer is hair thin, it is comparatively easy to remove therefrom the solvents contained therein and this removal will hardly interfere with the formation of a surface skin. If the matter to be treated is in the form of threads, as for instance, artificial silk threads, there is hardly any possibility of a surface skin being formed before the removal of these solvents. While a solvent charged atmosphere is necessary to prevent the formation of a surface skin, care must be taken never to completely saturate the atmosphereor allow the atmosphere to be completely and fully saturated, as the solvent vapors in such saturated atmosphere would react on the layer from which they were removed and would suddenly cause the layer to deliquesce. In my invention, the increase of pressure accompanied by an increase of temperature is utilized for the purpose of preventing complete saturation of the solvent charged atmosphere and for substituting for a portion of the solvent charged atmosphere an equivalent portion of heated fresh air. q

The resilient transparent layer to be applied to the glass sheets is under ordinary circumstances a resin polymerisation plasticiser and a solvent. Of course, however, I do not wish. to be limited to the use of my process with a layer of this particular character. v

While the mechanism which I have illustrated 'provides for the automatic withdrawal of a portion of the solvent laden air and the automatic admission of an equal portion of fresh air, yet I do not wish to be limited to this, as the valves '2 I and 30 may be operated by hand. 'It is to be particularly noted that if fresh air were constantly admitted and air was constantly withdrawn from within the chamber 3, there could be no increase of heat to thus increase the absorptive powers of the air. By intermittently withdrawing the solvent laden air or gas and intermittently admitting fresh heated air, however, I secure not only an increase in the absorptive powers of the air but also secure an increase in pressure whereby the valves may be automatically operated.

What is claimed is: a v,

1. A method of preventing the dellquescence of a resilient substance in solution applied to a sheet of glass, including the step of maintaining above the layer of substance a confined substantially quescent atmosphere charged with vapors of the solvent for said resilient substance for the purpose of preventing the formation of a skin on the surface thereof and gradually increasing the absorptive power of the atmosphere for the substance solvent by gradually increasing the temperature of the atmosphere.

2. A method of preventing the deliquescence of a solution of resilient material applied in a layer to a sheet of glass which includes maintaining the layer in a closed chamber with an atmosphere charged with vapors of the solvent for said material and maintained substantially quiescent to thereby prevent the formation of a skin on the surface of the layer and increasing the absorptive power of such atmosphere by gradually increasing the temperature thereof.

3. A method of preventing the deliquescence of a solution \of resilient substance applied as a relatively thick layer .to a sheet of glass, which includes maintaining above the layer a substantially quiescent atmosphere charged with the solvent for the substance and capable of taking up more of such solvent, increasing the absorptive power of the atmosphere by gradually increasing the temperature of the atmosphere and at determined intervals withdrawing a minor portion of said atmosphere and simultaneously adding fresh atmosphere thereto in a quantity sufiicient to replace that portion of the atmosphere so withdrawn.

4. A method of removing a solvent from a relatively thick layer of resilient substance applied to a sheet of fluid impervious material, which consists'first in placing the sheet with the layer thereon in a closed chamber containing an absorptive gas for the solvent of said substance, maintaining said gas in substantially quiescent contact with the layer, gradually heating the gas in said chamber to gradually increase its absorptive capacity and when the gas has reached a predetermined degree of saturation, then withdrawing a minor portion of the saturated gas from the chamber and simultaneously adding to the gas remaining in the chamber and charged 5. A method of treating a layer of resilient material in solution applied to a sheet of fluid impervious material to remove the solvent from said layer which consists first in placing the sheet with a layer thereon within 'a closed chamber having therein an absorbent atmosphere for the solvent of said resilient material, maintaining the at mosphere substantially quiescent in the chamber, gradually raising the temperature of the solvent absorbent atmosphere within the chamber to thereby gradually increase the absorptive power of the atmosphere, then utilizing the resulting increase of pressure to cause a minor portion of fresh atmosphere to be admitted to the solventladen atmosphere while withdrawing an equal portion of .the solvent-laden atmosphere therefrom until the pressure of the solvent-laden atmosphere within the chamber has been reduced to a predetermined lower point, and then maintaining the mixed fresh atmosphere and solventladen atmosphere substantially quiescent while gradually raising the temperature of the mixture to increase the absorptive power of the mixture.

6. A method of treating a layer of resilient material in solution carried on a sheet of fluid 10 absorptive power by relatively slight degrees and,

after the atmosphere is substantially saturated with the solvent vapors, removing a minor portion of the substantially saturated atmosphere from the chamber and introducing fresh atmosphere to the chamber having a temperature lower than that of the gas withdrawn and in an amount substantially equal to the amount removed to thus reduce the pressure and temperature of the atmosphere within the chamber.

ADOLF KAMPFER 

